Temperature increase of foods in car trunk and the potential hazard for microbial growth

This study assessed the potential microbial hazard posed by temperature increases on refrigerated and frozen food stored in car trunk exposed to sunlight. The internal temperatures in the trunk and of food items (egg, milk, tofu, fresh meat, and frozen meat) stored in it during summer were measured at 10 min intervals for up to 3 h (12:00 PM to 15:00 PM). Trunk temperature steadily increased from 32.3 °C up to 41.5 °C, with longer exposure times. Food temperature also increased substantially during this period, reaching 33.5 °C (frozen meat), 35.3 °C (milk), 35.6 °C (tofu), 37.0 °C (egg), and 38.4 °C (fresh meat). Cloud cover and solar radiation affected car and food temperature, with lower cover and higher radiation associated with higher food temperatures (7.1 °C higher in the car trunk when compared to a situation of extensive cloud cover and low radiation, and 6.9 °C higher for eggs, 5.9 °C for milk, 5.0 °C for tofu, and 7.4 °C and 5.5 °C for fresh and frozen meat, respectively). The temperature of refrigerated foods (egg, milk, and fresh meat) reached 20 °C within 40 min (tofu: 60 min) and 30 °C within 90–110 min (tofu: 130 min). The temperature of frozen meat reached to danger zone (5–60 °C), which is associated with bacterial growth, after 90 min. Consumers should therefore realize the importance of time–temperature control, particularly in warm and sunny weather. Purchased foods should be transferred to a refrigerated environment as fast as possible, and the car trunk should be avoided. The present results can be used for consumer education, contributing to the recognition of the importance of food safety.